Coaxial transmission line switch



March s, 1963 R. A. BRENNAN 3,080,539

COAXIAL TRANSMISSION LINE SWITCH Filed July 22, 1959 United StatesPatent O 3 @Sil S39 Coaxmr. 'rnANsit/nssrort anni swrrcrr Robert A.Brennan, rlorrance, Calif., assigner to Hughes Aircraft Company, CulverCity, Calif., a corporation of Deiaware Filed July 22, i959, Ser. No.829,187 2 Claims. (Cl. 3332-81) vThe present invention relates tomicrowave transmission means and more particularly to means forcontrolling the amount of attenuation between two sections of a coaxialtransmission line.

lt is frequently desirable in microwave systems when transmitting powerfrom one portion of a system to another portion to vary the amount ofpower so transmitted in response to the rate at which the system isaccelerating. Heretofore, it has been customary to accomplish this byemploying a so-called G switch containing ysome form of inertia elementresponsive to acceleration that controls a relay. The relay in turn isettectivc to insert or withdraw a microwave shutter into or o-ut of thetransmission line. As a result, the amount of attenuation of the powerin the `system will be varied in accordance with the acceleration in thesystem. However, such arrangements form bulky appendages to the systemand also necessitate an additional external power source and accordinglyare not entirely satisfactory.

it is an object of the present invention. to overcome the foregoingdifficulties by providing improved means that are responsive to the rateat which the microwave system is accelerating and are effective to varythe amount of attenuation between different portions of the system.

More particularly, this is to be accomplished by providing a couplingdevice for interconnecting two sections of coaxial transmission linethat includes a cylindrical outer conductor and an inner conductor. Atleast a portion of a center conductor is laterally movable andmechanically interconnected with a mass. Normally, the mass will bespring biased to retain the inner conductor electrically interconnectedwith the center conductors inthe adjacent sections of the transmissionline. This will thereby insure the maximum amount of coupling betweenthe adjacent portions of the system.

However, in the event there is acceleration in excess of somepredetermined amount and in a predetermined direction, the accelerationforces on the mass will overcome the forces of the spring. The mass willthen move the inner conductor so that it will become electricallydisconnected from the center conductors in the adjad cent sections oicoaxial lines. This will present a discontinuity to the flow ofmicrowave power through the coupling device. As a result, any powerpassing this discontinuity will have` to be propagated therethrough inawaveguidemode. Accordingly, it may be seen that by a proper selectionof the dimensions of the coupling device the amount of power attenuationmay be made the desired amount for the amount of acceleration present.

In the drawing, the FIGURE is a longitudinal crosssectional view of twosections ot a coaxial transmission line; connected together by means ofa coupling device embodying the present invention. v

Referring to the drawing in more detail, the present invention isparticularly adapted'or use in a microwave power transmission system lilincluding a first section of coaxial transmission line l2 and a secondsection of coaxial transmission line 14. Each of these sections 12 and14 includes a cylindrical outer conductor lo and lS and an innerconductor 26 and 22. The inner conductors 20 and 22 extend axiallythrough the conductors 16 and 1S. The ends Zit 4and Z6 of the conductorsice terminate substantially iiush with the ends of the sections l2 andt4 and are held in concentric spaced relation with the conductors i6 and13 by any suitable means.

The ends of the two sections l2 and t4 of coaxial line are connectedtogether by means of a coupling device Z8. The present coupling device28 includes a cylindrical outer conductor Sti that includes a threadedportion 36 and/or a threaded tting 3S. These are adapted to be attachedto corresponding sections on the ends of the two sections 12 and lli ofthe coaxial line.

The outer conductor 3b is hoilow so as to form a cylindrical passage It@therethrough that substantially recisters with the passages in the twosections "r2 and 14. inner conductor means are provided in this passage40 that includes two end portions d4 and i6 and a movable center portion43. The -two end portions te and 46 are preferably retained in iixedaxial alignment with the passage 4G by means of dielectric supports 5i).The outer ends of these portions 44 and t6 are positioned so as totightly engage the ends 24 and 26 o the inner conductors 2li and 22 andbe in intimate electrical contact therewith.

The inner ends 52 and 54 of the inner conductor portions are terminatedin spaced relation to each other so that an additional center portion 48will just fit therebetween. This center portion 4S is preferably mountedon a dielectric strut 56 that is slidably disposed in a pair of alignedopenings 58 in opposite sides of the outer conductor 3G. It may be seenthat as this strut 56 moves axially through the openings 53 the centerportion 43 will be moved laterally into and out of contact with theinner ends 52 and 54 of conductor portions 44 and 46. The ends 52 and 54of the conductors are preferably stepped or otherwise tapered so as tominimize reflections. lt may also be desirable to provide an alignmentpin do that is secured to conductor dit and projects through conductort8 to thereby insure the center portion 48 being maintained properlyaligned with respect to the end portions.

A generally cylindrical mass 62 is titted around the exterior of theouter conductor 3o for sliding axially thereon. it is desirabie for apair of shoulders 64 and 66 to be provided on the conductor Sti so as toform stops that effectively limit the amount of axial movement of themass o2.

The interior of the mass 62 preferably includes double Icam surfaces 68and 70 that receive the opposite ends of the strut 56. It will be seenthat the double cam surfaces 68 and '7h will hold the strut 56therebetween and positively control the lateral position of the centerportion 48. It has been found desirable for one of the cam surfaces 74)to include a spring biased section such as a pivoted lever 72. This willprovide sufcient lost motion to eliminate mechanical interference thatmight otherwise prevent a proper electrical contact being made betweenthe ends of the various portions 44, 4o and 48 of the center conductor.A spring 74 may be provided for resiliently forcing the mass 62 axiallyagainst one of the shoulders so as to normally retain it in thisposition. In the present instance the spring 74 retains the mass againstthe shoulder 64 so that Iall portions 44, 46 and 48 ot the innerconductor are retained lin good electrical contact.

However, in the event there is axial acceleration of the system 1li in adirection of the arrow in the drawing, the mass 62 will tend to compressthe spring 74 and move axially along the exterior of the conductor Siltoward the other shoulder 66. This will simultaneously move the centerportion i8 laterally of the passage 40. It should be noted that the camsurfaces 68 and 70 may have any aosdssa desired pr'olile to impart therequired lateral movement to the center portion 48. However, it isdesirable for both end portions of the cam surfaces 68 and 76 to bestraight and substantially parallel to the axis of the coupling unit soas to form dead areas. Thus, even though there may be small vibratorymovements of the mass 62 of the center portion 43 Will not subject toany lateral vibrations.

Normally, the entire microwave system will be at rest and the spring 74will resiliently retain the mass '72 against one of the shoulders 64.The opposite ends of the strut 56 will engage the end portions of thecam surfaces 68 and 70 and consequently will be forced toward the a-xisof the passasge 40 through the center of the coupling device 28. Theends of the center portion 4S will thus be carried against the 'endportions 52 and 54. The combined 'action of the alignment pin 60 and thekspring biased portion of the cam surface 70 will insure allportions 44,46 and 48 being retained in intimate electrical contact. Any microwavepower present in the system 10 will thus be free to travel from onesection 12 or 14 of the coaxial transmission line to the other vsection14 o-r 12, respectively, with virtually no discontinuity. As a'result,there will be little or no loss in the amount of power owingtherethrough.

However, if the system 10 is subjected to an acceleration having -acomponent in the direction of the arrow, the inertia of the mass 62 willcause 4it to slide axially along the exterior of the outer conductor andcompress the spring 74 The amount of this movement of the mass 62 alongvthe axis of the coupling device 28 will of course be a function of theamount of acceleration. After some predetermined level is reached theends of the strut .56 will have traversed the level portion of the camsurfaces 68 and 70. At thisp'oint, any additional acceleration willcause the vstrut 56 to slide through the openings 58 and carry thecenter -portion 4S laterally therewith. When this occurs the ends 52a-nd 54 of the various portions 4 4, 46 and 48 will be moved out ofelectrical contact so 4that the ovv of current therethrough will bedecreased. As the acceleration increases, the amount of lateral movementof portion 43 will increase until the ends of the strut 56 are riding onthe other straight portions of the cam surfaces 68 and 70 and the centerportion 48 is moved to the side of the passa-ge 40. At this point .therewill be no direct electrical connection between the two portionsk44 and46 'and a marked discontinuity will exist in the transmissoin path.

Under these circumstances, any microwave power that passes from onesection 12 'or 14 to the other will have to be propagated across theresultant discontinuity in a circular waveguide mode 'along theconductive surface of the passage 40.' Thus the microwave power will becoupled from one coaxial section 12 or Y14 into the circular waveguidesection formed by passage 4t) and then coupled back into the othercoaxial section 14 or 12, respectively. It is of course apparent that bya proper selection of the various physical dimensions of the sections 12and 14 and the coupling device 28, any desired amount of attenuation ofthe microwave power may be obtained when there is an accelerationpresent in the system v1tl.

vWhile only a single embodiment of the invention has.

been illustrated and described it will be readily apparent to thoseskilled in the art that numerous modifications and different embodimentsmay be employed. For example, the inertia mass may be made responsive toaccelerations in any direction and the attenuation may be m-ade to occurduring conditions of no acceleration.

" (b) a dielectric pin extending through 'the hole in What is claimedis: 1. A microwave inertia switch comprising: (a) a coaxial transmissionline having an outer conductor and an inner conductor, an elongatedsection of said inner conductor being movable in a direction transverseto the axis thereof, said outer conductor having ahole therein adjacentthe movable section of said inner conductor, said movable section havingstepped portions atthe ends thereof engaging in an overlappingyrelationship Acorrespondingly stepped ends of the remaining sectionslof `said inner conductor, said inner conductorhaving a hole extendinglthrough the overlapping stepped portions at vone end 'of said movablesection; l the overlapping stepped portions of said inner conductor;v(c) an elongated dielectric v'strut rigidly engaging the movablesectionof said inner'conductor land having v'an end extending'throughthehole in said outer conductor; I

' (d) Vand a mass movably disposed on the exterior of Asaid outerconductor and havingV a-n internal -cam surface contacting the end of"said dielectric nstrut "extending through the hole insaid outerconductor, -said cam surface being contoured in a predetermineddirection to cause movementof `said strut in a direction transversetothe axis rof .said transmission line as said mass is moved in saidvpredetermined direction. 2. A microwave inertia switch comprising:

(a) a coaxial'transmission line having an outer conductor and an innerconductor, an elongated section of said inner conductor being movable ina direction transverse to lthe axis thereof, lsa-id outer conductorhaving a pair of holes, each disposed on diametrically opposite `sides*of the movable section of lsaid inner conductor, rsaid movable Isectionhaving stepped portions at 'the ends thereof engaging in 'Vanoverlapping relationship correspondingly stepped ends of the remainingsections of said inner conductor, said inner conductor having a holeextending through the overlapping stepped portions at one end of saidvmovable section; v

(b) 'a dielectric pin extending through the rhole in the overlappingsteppedportions of said inner conductor;

' (c) an elongated dielectric strut rigidly 'engaging the movablesection of 'said inner conductor and having ends extending through theholes in said outer conductor;

(d) a vmass encircling said outer conductor and havin-g double internalcam surfaces contacting the ends 4ot' said dielectric strut, said camsurfaces being complementally contoured in a direction valong the axisof said transmission line to cause -movement of said strut in adirection transverse to the axis-of said transmission line as said massis moved in a direction parallel to the axis thereof; l

(e) and an elastic member affixed to the exterior of said transmissionline and in engagement with said mass for restraining motion lthereof ina direction parallel to the axis of lsaid transmission line.

References Cited in the Yiile of this patent UNITED STATES PATENTS2,771,529 Kostriza Nov. '20,1956

1. A MICROWAVE INERTIA SWITCH COMPRISING: (A) A COAXIAL TRANSMISSIONLINE HAVING AN OUTER CONDUCTOR AND AN INNER CONDUCTOR, AN ELONGATEDSECTION OF SAID INNER CONDUCTOR BEIN